Method of treating and finishing cellulose and cellulosic fibers and products



Patented Aug. 19, 1941 UNITED STATE S PATENT OFFICE METHOD OF TREATING AND FINISHING CELLULOSE AND GELLULOSIC FIBERS AND PRODUCTS No Drawing. Application September 12, 1938, Serial No. 229,522

4 Claims.

This invention 'relatesto methods of treating cellulose and more particularly to methods of treating and finishing cellulosic textile fibers,

either in the woven or unwoven form.

' structure in accordance with the novel methods and steps hereinafter set forth.

Broadly the invention contemplates treating cellulosic material with the hydroxides of the variousalkaline earth metals, such as calcium hydroxide, strontium hydroxide, lithium hydroxide, and more particularly barium hydroxide, alone or in conjunction with other reagents.

As previously pointed out, the quality of cellulosic material may be improved by treatment with barium hydroxide without employing other reagents. For example, the cellulosic material may be first wet on or boiled and then immersed in a solution of barium hydroxide for a few minutes. The excess solution is then removed irom the material by any well-known method and the material is then subjected to a series of washes in boiling water, until the water indicates the presence of a very slight amount of alkali or the absence of any alkali. To remove all traces of barium compounds the material may be dipped in a very dilute solution of acid in which the barium compounds are soluble, such as hydrochloric or acetic acid, and then the material is washed until free of acid and dried. If the material is washed sufficiently in boiling water to free it of alkali the acid treatment is not necessary. Pressure washes will reduce the number of washes necessary to free the material of alkali. If the material is treated in a barium hydroxide solution at temperatures of 65 C. or higher, the first boiling wash water immediately becomes yellow and somewhat similar to the color of the water in which the material was boiled before the barium hydroxide treatment, but has a richer and deeper shade. Satisfactory results have been obtained by employing a barium hydroxide solution at room temperatures but it is preferred to maintain the barium hydroxide solution at temperatures from 60 to over 100 ce'ntigrade during the treating period.

It is important that the wash waters employed after the barium hydroxide treatment be boiling since it has been found that when merely hot water is used the tensile strength improvement in the finished product is not nearly so marked. The tensile strength of the cellulosic fibers increases progressively with the degree and number of boiling water washes until the alkali compounds have been substantially completely removed by these washes.

It is believed that barium compounds that are slightly water-soluble are formed in the reaction between barium hydroxide and thedesser celluloses and other impurities and that these barium compounds may be very satisfactorily removed by a series of washes in boiling water, resulting in a cellulosic product having greatly increased tensile strength and porosity.

The improved method may be practiced with the material under tension, or the material may be driedunder tension or both. Furthermore, the treated material may be subsequently treated under tension in strong alkali such as potassium hydroxide or sodium hydroxide (such as mercerizing) to further increas the tensile strength, appearance and dye affinity of the material.

A modification of the invention provides a method of treating cellulosic yarns, threads, fabrics and the like, to make them substantially unshrinkable in laundering, that is, the material will subsequently retain the dimensions set therein during treatment. It has been found that the dimensions of the material can be stretched up to 24 per cent of any one dimension, or up to 12 per cent of both dimensions, during treatment and, accordingly, that the original area will be retained when the material is subjected to the customary washings. Cellulosic material treated in accordance with the method herein described shows no shrink in warp or weft directions when subjected to repeated laundering operations and also retains the finish received during treatment.

It is to be understood that the terms cellulosic material or cellulosic textile fibers include any fiber or admixture of fibers, whether natural or synthetic, in which the chief constituent of the fibers is or was cellulose, and any mixture of animal and cellulosic fiberswherethe improvement of the cellulosic fibers improves the appearance, handle or strength of the mixture. These terms include all cellulosic fibers, whether they be in the form of fabrics (knitted or woven), yarn, cords, threads, fibers and coverings.

The invention will be readily understood from the following specific example in which certain preferred methods of employing the invention are given, illustrating the wide range of methods by which the invention may be applied and the various effects that may be obtained by such methods.

Example Cellulose textile fibers, preferably in the grey state, and which have preferably been first wet known method) are treated in a 50 gram per litre solution of barium hydroxide at a temperature of from 60 to over 100 degrees centigrade for 1 to 30 minutes (dependent upon the temperature, or until the fibers have been thoroughly saturated in the aqueous barium hydroxide solution; if the fibers. have not already been wet out or boiled oil. it is preferred to boil the barium hydroxide solution). The fibers are then squeezed or centrifuged to remove the excess solution, and then washed in a series of boiling water washes, comprising substantially pure water such as distilled water, until substantially completely free of alkali and slightly watersoluble barium compounds. The number of boiling water washes depends upon the degree of efficiency of the wash, upon the ratio of water to cellulose, and upon whether the washes are under pressure, such as may be applied in a kier, or whether a counter-washing system is used. In washing out in an open vessel, with a ratio of parts of water to one of cellulose, we have found it necessary to wash the material as many as ten times to remove the alkali and reaction products, and then immerse it in very dilute acid. The fibers being substantially free of alkali hydroxide compounds it is safe to use any of the well-known commercial acids, even sulphuric acid; however, if it is desirable to be certain that not even a trace of insoluble barium sulphate be present, acetic or hydrochloric acid may be used. -It is preferable to use these acids in a very dilute state, such as from 1 to grams per litre. The acid is then removed by water washes, and the fibers dried with or without tension as desired.

If the fibers are substantially free of alkali it is not necessary to acidify them, however, we prefer to do so.

In commercial practice on a warp mercerizing machine, the yarn or other material being treated is placed under tension before treatment in order to keep the fabric or yarn from backlapping around the squeeze rolls.

The material may be mercerized before or after the barium hydroxide treatment, according to any of the well-known methods of mercerizing.

It has been found that subsequent mercerization under tension further improves to a limited extent the tensile strength, lustre and general appearance, and affinity for dye-stufis of cellulosic material treated in accordance with the invention and this improvement, more particularly that of tensile strength, is considerably greater than if the fibers had merely been mercerized under tension without having first been treated according to the above-described methods.

Very satisfactory results have been obtained by substituting calcium, strontium or lithium hydroxides for barium hydroxide in the examples given in concentrations up to the limits of their respective solubilities, depending upon the temperature of the water, but the most satisfactory results to date in improving the qualities of cellulosic material, as hereinbefore mentioned, have been obtained by employing barium hydroxide in the manner described.

It is therefore understood that the foregoing examples setting forth specific materials, weights,

and proportions, are given for the purpose only aaeavao of illustrating the invention, and that, our invention is not limited thereto but contemplates such other and further modifications and changes which may become apparent to those skilled in the art, and which are inherently possessed herein. For instance, hereunder are some of the concentrations which may be employed:

The concentration of barium hydroxide alone. These concentrations also apply when the hydroxides of calcium, lithium, and strontium are employed. The acids employed are diluted to a point which will not cause tendering of the fibers.

The matter of concentration of the reagents is governed by the degree of treatment desired, by the nature of the desired finished product, and also by the manner in which the treatment is applied physically. Further, the nature of the cellulosic fiber before treatment governs the concentration of the barium hydroxide and similar hydroxides to some extent; for example, whether it is Egyptian cotton or American cotton; whether it is in the bleached, grey, kiered, or mercerized state, as mentioned in a previous paragraph.

What we claim is as follows:

1. The method of treating natural cellulosic textile material to improve the quality thereof, which comprises saturating the material with a barium hydroxide solution comprising approximately a 50 gram per litre solution of barium hydroxide (Ba(OH)2:8H2O), removing the excess hydroxide solution, and then subjecting the impregnated material to a series of washes in substantially pure water at a temperature ofapproximately C. or over to substantially completely remove the'alkali and barium compounds.

2. The method of treating natural cellulosic textile material to improve its quality, comprising placing such material under tension, saturating said material under tension with a solution of barium hydroxide, subjecting said material to a plurality of washes in boiling distilled water suficient to remove substantially completely unreacted barium hydrovide and barium compounds, and drying said material before releasing the tension.

3. The method of treating natural cellulosic textile material to improve the quality thereof, Which comprises immersing said material in a solution of barium hydroxide comprising approximately a 50 gram per litre solution of barium hydroxide (Ba(OH)2:8I-I2O), removing the excess solution and washing said material approximately ten times in boiling distilled water, each wash comprising approximately ten parts of water to one of cellulosic material.

4. The method of treating natural cellulosic textile material to improve the quality thereof which comprises removing to a great extent the impurities in the cellulosic structure which tend to weaken it by saturating said material in an aqueous solution of barium hydroxide at a temperature between 60 and 100 C. and removing the alkali and reaction products by subjecting the material to a plurality of washes in boiling distilled water.

ERIC OWEN RIDGWAY. FREDERICK CURTIS TUCKER- 

